Patent GB-531388-A (GB)
Title: Improvements in or relating to control or regulating devices such, for example, as automatic pilots for craft
IPC: G05D1/00
Filed: 1939-03-28
Abstract: 531,388. Fluid-pressure servomotor-control systems. SPERRY GYROSCOPE CO., Inc. March 28, 1939, No. 9681. Convention date, April 5, 1938. [Class 135] A control or regulating device for the automatic control of a control surface of a dirigible craft comprising a pneumatic pick-off associated, for example with a gyroscope, said pickoff comprising two members relative displacement of which produces a pressure difference applied to a relay valve by which the craft is controlled, one of said members being adapted to follow up the other under the influence of said pressure has means for retarding the follow-up movement. The invention is shown in Fig. 1 applied to a gyro-vertical located in a casing 1 continuously evacuated through a pipe 2. A horizon bar 8 visible through a window 9 is connected to the rotor casing 3 through a pivoted arm 10 as described in Specification 393,695, [Group XX]. An extension 17 of the gimbal ring 6, which lies in the fore-and-aft axis of the craft is connected through gearing 15, 16 and a shaft 14 to one of the relatively displaceable members which in this case is formed as a semi-circular segment 13 which in its central position obturates equally ports 21, 22 in a casing 18 evacuated through a pipe 23. The ports 21, 22 are connected by pipes 24, 26 to the chambers 37, 38 of a relay valve 25 similar to that described in Specification 515,290. The pipes 24, 26 are also connected through pipes 33, 34 having adjustable throttles to a casing 30 divided by a diaphragm 31 into two chambers having adjustable leaks 71, 72. Variable leaks 36, 36<SP>1</SP> are also provided in the pipes 24, 26. On movement of the shutter 13 from its central position, a differential pressure is created in the pipes 24, 26 and this operates the pistons 51, 51<SP>1</SP>, 52 of the relay valve 25 which controls a servomotor 29 operating a control surface 85. The differential pressure also builds up slowly in the casing 30 so that the diaphragm 31 acting through the rod 39 and a spring-centralized lever 41 returns the shutter 13 and casing 18 to their original relative positions before the craft returns to its original attitude. By means of byepass passages 56, with or without spring-pressed ball valves 55, and restricted orifices 57, the oil pressure supplied through a pipe 45 to one side or other of the servomotor is permitted to build up behind the piston 51, or 51<SP>1</SP> until it balances the differential air pressure in the diaphragm chambers 37, 38. By this arrangement the movement of the control surface is rendered proportional to the course deviation and inversely proportional to the air speed. The pitch control is effected in a similar manner by a piston valve 60 lying along the fore-and-aft axis and operated through arms on shafts 12, 63 from the arm 10. The valve 60 through pipes 69, 70 operates the pitch relay valve, the said pipes being connected also to the opposite sides of a diaphragm 31<SP>1</SP> similar to the diaphragm 30 and operating through a lever 73 to return the valve seat 68 to its original position relative to the valve 60. Adjustment of the angle of pitch is effected by a thumb screw 76 acting on the lever 73 whilst the banking adjustment is made by a thumb screw 78<SP>1</SP> acting through a cam 79<SP>1</SP> on the lever 41.